Prior art vinylidene fluoride base fluororubbers are used in a variety of applications mainly in the automobile and mechanical industries since they produce elastomers having good heat resistance and mechanical strength.
These fluororubbers, however, are not satisfactory in chemical resistance. They are readily swollen in polar solvents such as ketone, lower alcohol, carbonyl and organic acid solvents. They are deteriorated by amine-containing chemicals so that their rubber strength and elongation may substantially decline. With respect to low-temperature properties, the fluororubbers lose rubber elasticity at temperatures below -20.degree. C. to such an extent that they cannot be used as sealants. This generally imposes a limit on the use of fluororubbers in cold areas.
In order to eliminate these drawbacks, curable fluorine-containing compositions comprising a perfluoro compound and a fluorinated organohydrogenpolysiloxane as main components were proposed. These compositions, however, are liquid because they are based on liquid perfluoro compounds having a low degree of polymerization. Then the compositions are suitable in the FIPG process and LIMS molding, but less effective in compression molding conventionally employed for rubber molding.
In particular, the curable fluorine-containing compositions often prohibit the use of conventional two-plate molds for rubber because of the difficulty of molding and the frequent occurrence of defects by air entrainment. Steady production is difficult unless a special LIMS mold is newly fabricated. The LIMS mold, however, has the problems that it is generally more expensive than the conventional two-plate molds for rubber, the mounting of the mold in a LIMS molding machine is cumbersome, and the molding machine requires time-consuming adjustment after mold mounting. The LIMS mold does not lend itself to the manufacture of a variety of parts in small quantities.